The International Bone Marrow Transplant Registry (IBMTR) is a collaborative study group that has been conducting research for the past 20 years in an effort to improve the success of allogeneic bone marrow transplants. At present over 200 (about 70% of all) transplant teams in the US and abroad voluntarily contribute detailed information regarding their consecutive allotransplant recipients to the IBMTR. The IBMTR database includes records for more over 16,000 recipients of allogeneic and syngeneic transplants. The North American Autologous Bone Marrow Transplant Registry (NAABMTR) is a similar group, formed in 1989, including 90 institutions in the US and Canada that contribute data regarding consecutive autotransplants. The NAABMTR has registered autotransplants. In this five-year Program Project renewal application, the Advisory Committees of the IBMTR and the NAABMTR request support for a statistical Core Component that is required by and shared solely within the proposed research program. Support also is requested to conduct studies designed to address important issues in allogeneic and autologous transplants that would be difficult or impossible for single institutions to address but which can be investigated using data from multiple centers. Project I focuses on transplants for leukemia, Project II on transplants for Hodgkin and non-Hodgkin lymphoma, multiple myeloma and breast cancer. Issues addressed include patient and disease factors predicting outcome, optimal transplant strategies, whether reinfused cancer cells cause relapse after autografts, relative efficacy of allogeneic and autologous transplants and relative efficacy of transplants and d=conventional chemotherapy. Project III focuses on issues common to transplants for several diseases, ie. use of T-cell depletion to prevent graft-versus-host disease after allografts and impact of cytokines on outcome of allo- and autografts. Completion of these projects is facilitated by data management, statistical and organizational resources provided by the Core.